Self-extinguishing fuse link



Jam 7 1947. R. R. PITTMAN SELF-EXTINGUISHING FUSE LINK 2 Sheets-Sheet 1 Filed July 17, 1944 |NVENTOR @44' @V7 Jan- 7, 1947. R. R. PITTMAN SELF-EXTINGUISHING FUSE LINK Filed July 17, 1944 2 Sheets-Sheet 2 Fig. 6

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25 INSULATION FLEXIBLE `14 INVENTOR Patented Jan. 7, 1947 UNITED STATES PATENT OFFICE 2,413,887 ASELF-EX'AINGrUISHING FUSE LINK Ralph R. Pittman, Park Hill, Application July 17, 1944, Serial No. 545,293 Claims. (Cl. 20G-120') This invention relates to fuse links, and more specifically to a tensioned fuse link having a fusible element combined with means for extinguishing an arc which may follow the fusing of the fusible element.

Among the objects of the present invention may be noted the provision of a fuse link in which the fusible element connects separable conducting members within a flexible and expansible sleeve of insulating material so that any arc which follows the fusing of the fuse link will be confined within the flexible tubular insulator and its extinguishment facilitated thereby; the provision of a fuse link which by virtue of its self-extinguishing features makes unnecessary the use of the auxiliary expulsion fuse barrels now commonly in use; the provision of a fuse link requiring support only at its upper end when in the service position; and the provision of a fuse link which is simple in construction and easily assembled.

The elements and combinations thereof, features of construction, and arrangement of parts which comprise ythe invention will be exemplified in the description to follow, and the scope of the invention will be indicated in the appended claims.

The accompanying drawings illustrate two possible embodiments of the invention. Fig. 1 is an elevational View of one form of the invention; Fig. 2 is a sectional View of the fuse link shown in Fig. 1; Fig. 3 shows in elevational View the appearance of the fuse link of Fig. 1 following the fusing of the fusible element; Fig. 4 is a section along the line i-Ii of Fig. 3; Fig. 5 shows in* section another form of the invention; and Fig. 6 shows in elevation the appearance of the fuse link shown by Fig. 5 following fusing of the fusible element.

It is well known that heretofore fuse links were not designed for or regarded as effective circuitinterrupting devices, and therefore were cornmonly installed in expulsion tubes to provide the desired interrupting ability. One purpose of the present invention is the provision of a self-extinguishing fuse link which is suitable for use in the type of fuse construction shown in Patent No. 2,356,352, dated August 22, 1944, granted to Ralph R. Pittman. It may be noted that the fuse link in the structure referred to is tensioned, and it will be observed that the fuse link of the present invention has certain advantages in operation when tensioned either by resilient means or gravity.

Referring in detailtq the drawingsparticuelement I 2 .1'S-.ur1filsedl larly to Figs. 1 toA 4 inclusive, the numeral IQ designates a tubular container l0, of conducting material. The upper end of the container Ill is provided with an outwardly flanged closure for convenience in connecting the fuse link in an electric circuit. The closed end of the container may conveniently form the upper terminal of the fusible element I2, by pressing the upper end of the latter into the metal of the container. The fusible element I2 extends coaxially downwardly to a point near the lower end of the container I3, and the lower terminal of the fusible element I2 is formed as a connector I3, which joins the flexible copper cable I4 to the fusible element I2.

The tail I the connector I3, and the fusible element I2 forni a normally tensioned member the ends of which are respectively fastened to the tubu'larcontainer IQ and the conducting terminal member 20, the-rivet I9 providing the means for rigidly fastening the tail I 'l to the member 2d. When the member I Il is supported in the operating position, the member 28 is released for downward movement away from the member Ill when the fusible element fuses. rl`he insulating bushingV IB/is Vtightly pressed intothe open end of the container lli, and the normally tensioned member extended therethrough for the purpose of avoiding contact of the latter member with the wall of the container IG. An opening 2l in the lower conducting member 2; is provided for use with a terminal bolt of some associated apparatus. As will later be apparent, the above-described organization is only one of several structures embodying a fusible element which is suitable for use in the construction of thepresent invention.

A flexible tubular insulator I I is fitted over the wall of the container Il), and fastened thereto at its upper end by crimpingthe head of the container intol the sleeve Il as indicated at the reference character I'l. At its lower end, the tubular insulator or sleeve I I is rigidly fastened to the lower conducting member 2i) by means of the rivet I9. The insulating material from which the tubular insulator I I, is formed is preferably one which is both resilient and flexible, and rubber-like, materials, fory example, plasticised polyvinyl chloride orvarious types of synthetic rubber are suitable for use in carrying out the invention.

The form of the inventionillustrated by Figs. i to 4 inclusive shows the tubular insulator I I folded into a series of circumferential pleats, the normally tensioned member holding the tubularinsulator in collapsed shape when the fusible 'I`h e tail Hlof the tensioned member is extended through an opening l in the wall of the tubular insulator Il at a point near its lower end, the distance between the conducting members lil and 2Q being relatively short in comparison to the expanded length of the tubular insulator. Preferably the opening l5, and the length of the'folded portion indicated at the numeral i6, are so related to the length of the tail I4 that the connector l3is not entirely withdrawn from the tubular insulator H when the fusible element l2 fuses and the elements assume the positions indicated in Fig.

3. The purpose of so relating the elements is to provide a construction in which any circuitinterrupting arc which may follow the fusing of the fusible element will be elongated between the fusible element terminals while contained within the expansible tubular insulator. The extinguishment of the arc is thereby facilitated, by its confinement, and as an additional advantage, the arc will not be blown into contact with any live parts of contiguous apparatus.

If the material of the tubular insulator li is Vso chosen that it is inherently resilient, the

folded insulator will act to continuously urge the conducting member 2E] away from the tubular container le, movement of the member 23 being normally restrained by the tensioned member and released when the fusible element fuses. It may be noted that the construction is such that gravity urges the member 2li downwardly when the container lil is supported at its top or the button-head of the link, so that it is not essential that the material of the insulator H is resilient; any suitable flexible material may be used.

The form of the invention illustrated at Figs. 5 and 6 differs from the form previously described with respect to the configuration of the folded tubular sleeve or insulator. In the construction shown in Figs. 5 and 6, the opening 23 of the flexible tubular insulator 22 through which the tensioned member extends is relatively close to its upper end, resulting in a longer folded portion between the opening '23 and the lower conducting member 2i. When supported from its upper end in the normal service position, the appearance of the device following the fusing of the fusible element l2 is shown at Fig. 6.

The single fold construction has the advantage of lower cost, and lacks the advantage present in the pleated construction of arc elongation within the tubular insulator. The less expensive construction is well adapted for use in situations in which only small amounts of arc-energy are involved.

From the description it may be Seen that the several objects of the invention are achieved with attendant advantages. It is recognized that many changes may be made in connection with the above-described constructions within the scope of the invention, and it is therefore intended that the description and drawings will be regarded as illustrative rather than limiting.

claim as my invention:

l. A fuse link comprising an upper conducting member, a lower'conducting member spaced therefrom, a fusible element connecting said members, and a normally folded tube of insulating material joining said members, said fusible element when unfused holding said folded tube in folded shape and releasing said tube for unfolding when fused.V

2. A fuse `link comprising spaced conducting members, an elongated tube of folded flexible 4 insulating material joining said members, and means including a fusible element within said tube for holding said tube in folded shape, said fusible element normally connecting said conducting members and releasing said tube for unfolding when fused.

3. A fuse link comprising longitudinally spaced conducting members, a longitudinally expansible tube of flexible insulating material joining said members, and a fusible element within said tube connecting said members,V said fusible element restraining expansion of said expansible tube when said fusible element is unfused.

Li. A fuse link comprising relatively separable spaced conducting members, said members including an upper member and a lower member adapted for movement away from the upper member, a conducting member including a fusible element normally connecting said members and normally restraining their separation, and a tubular ilexibie and expansible insulating member joining conducting members and containing said fusible element, said insulating member having an expanded length greater than the normal distance between said spaced conducting members.

5. A fuse link comprising spaced conducting members, a normaily longitudinally pleated expansible tube of insulating material joined to said conducting members, and a fusible element normaily connecting said members and restraining expansion of said expansible tube, said tube being adapted to elongate when said fusible element fuses.

6. A fuse link comprising a tubular container of conducting material, a conducting member longitudinaliy spaced therefrom, a fusible element connecting said container to said conducting member, and an expansible tube of insulating material joining said container to said conduct ing member, said expansible tube being formed into a series of pleats extending along the outside wall of said container.

7. A fuse link comprising relatively separabie spaced conducting members, said members including an upper member and a lower member adapted for movement away from upper member, a normally collapsed longitudinally expansible tubular insulator having an expanded length greater than the distance between said spaced conducting members, means fastening said tubular insulator at its respective ends to the upper and lower conducting members respectively, and a tensioned conducting member including a serially related fusible element connecting said conducting members and holding said tubular insulator in the collapsed configuration, at least that portion of said tensioned meinber which includes said fusible element extending within said tubular insulator.

8. A fuse link comprising relativelyv separab spaced conducting members, said members in cluding an upper member and a lower member adapted for movement away from said upper member, a normally collapsed longitudinally expansible tubular insulator having an expanded length greater than the distance between said spaced conducting members, means fastening said tubular insulator at its respective ends to the upper and lower conducting members respectively, an opening formed in the wall of said tubular insulator between the ends thereof, and a tensioned conducting mem er including a serially related fusible element connecting said conducting members and holding said tubuluar insulator inthe collapsed configuration, said tensioned member extending from the upper conducting member Within said tubular insulator and through said opening outside of said tubular insulator to the lower conducting member, at least that portion of said tensioned member Which includes said fusible element extending Within said tubular insulator.

9. In a fuse link, a fusible element having spaced terminals the separation of which is adapted to increase when said element fuses, a single piece flexible and expansible tubular insulator, and means responsive to the fusing of said element for causing the increased separation of said terminals to occur within said tubular insulator.

10. In a fuse link, a fusible element having spaced terminals the separation of which is adapted to increase when said element fuses, a single piece flexible and expansible tubular in sulator, and means responsive to the fusing of said element for concurrently causing expansion of said tubular insulator and increased separation of said terminals within said insulator.

RALPH R. PITTMAN. 

